1. Field of the Invention
The present invention relates to a monitoring apparatus for an inkjet head, and more particularly, to a monitoring apparatus for an inkjet head, capable of sensing the vibration of the inkjet head after the ejecting of ink, to thereby defect whether the inkjet head is defective and to detect whether a head driver is abnormal, based on vibration waveform in the inkjet head.
2. Description of the Related Art
Recently, a piezoelectric type of inkjet head has been used for an industrial inkjet printer. For example, the piezoelectric type of inkjet head is used to directly form a circuit pattern by spraying ink produced by melting a metal such as gold, silver or the like onto a printed circuit board (PCB), create industrial graphics, or to manufacture a liquid crystal display (LCD), an organic light emitting diode (OLED), a solar cell, or the like.
This piezoelectric type of inkjet head may include a pressure chamber, a nozzle, a flow path, and a piezoelectric actuator generating driving pressure. In general, the piezoelectric actuator is closely adhered to an outside portion of the inkjet head corresponding to the circumference of the pressure chamber. By the change in displacement of the piezoelectric actuator to which an electric signal is applied, pressure generated by the piezoelectric actuator is transferred to the pressure chamber, so that a liquid droplet is ejected from the nozzle.
However, since the nozzle of the inkjet head is exposed to the air, the air may tend to flow into the inside of the head through a surface of the nozzle on which ink and the air come into contact with each other. This inflow of air may greatly reduce pressure generated by the piezoelectric actuator and cause the ejecting of the liquid droplet from the nozzle to be stopped. Like this, since the abnormal ejecting of ink may significantly affect the quality of the printing being performed, it is important to promptly detect a nozzle from which ink is being abnormally ejected.
The piezoelectric actuator receives an electric signal and converts the received electric signal into pressure, in order to eject ink from the nozzle. Conversely, when receiving pressure from the outside, the piezoelectric actuator generates an electric signal. Therefore, a piezoelectric element used as the piezoelectric actuator may also be used as a sensor capable of determining whether ink is being normally ejected from the nozzle by sensing the vibration of the inkjet head after the ejecting of ink.